Green Space Type and Healthy Ageing in Place: An Australian Longitudinal Study

Abstract

There is a lack of research on the long term association of green space types with a person’s healthy ageing score (HAS). We investigated the association of continuous exposure to green space types such as grass, low-lying vegetation, and tree cover on healthy ageing, including its functional capacity and resilience dimensions, while accounting for relocation. This is a  longitudinal study of a cohort of 22,715 New South Wales residents aged over 45 who participated in the Sax Institute’s 45 and Up Study living in Sydney, Wollongong and Newcastle.  Green space exposure was measured by tree canopy, low-lying vegetation and open grass percentage within 1.6-km road network distance buffers at baseline and second follow-up. Healthy ageing outcomes included functional capacity, resilience and HAS. Longitudinal models of healthy ageing on green space types were fit with controls for socioeconomic confounders. Women who did not relocate were associated with a lower functional capacity (β; 95%CI: -0.10; -0.15,-0.05) and higher resilience (0.11; 0.08, 0.14) compared to those who relocated. Apart from age, personal characteristics did not explain the variation in healthy ageing outcomes for participants who moved. For participants who did not relocate, grass cover of 30% was associated with a decreased functional capacity (-0.22; -0.41,-0.04) and HAS (-0.31; -0.56,-0.05). Also, 5-9% low-lying vegetation was associated with a decline in the functional capacity (-0.09; -0.15, -0.03) and HAS (-0.09; -0.17, -0.01) of participants who stayed but improved the resilience (0.28; 0.01, 0.55) of participants who relocated. Green space comprising over 30% tree cover appears to be most beneficial for functional capacity (0.42; 0.31, 0.53), resilience (0.19; 0.13, 0.25) and HAS ( 0.60; 0.45, 0.75). For participants who relocated, over 30% tree canopy was associated with improved functional capacity (0.33; 0.54, 0.62) but not resilience or their HAS.I ncreased neighbourhood tree canopy is beneficial for healthy ageing.

Keywords: green space, tree canopy, resilience, functional capacity, healthy ageing score